Authorities have ruled that 41-year-old physician Autumn Klein's cause of death was cyanide poisoning.

It was not immediately clear whether Klein's husband, Robert Ferrante, had retained representation.

Klein was a physician and former head of women's neurology at the University of Pittsburgh Medical Center. She died on April 20.

Officials said Ferrante was apprehended by West Virginia State Police after his car was stopped while heading north on Interstate 77 near Beckley, West Virginia.

Ferrante is a researcher and professor of neurological surgery at the University of Pittsburgh. He has been placed on immediate and indefinite leave, according to John Andrew Fedele, a school spokesperson.

As part of his position there, Ferrante managed a laboratory where he conducts trials of various drugs and chemicals, according to a criminal complaint.

On April 17, Allegheny County 911 dispatch received a call from Ferrante requesting medical assistance for his wife, who he said was possibly having a stroke, the complaint read. He described her condition as "conscious and breathing, but not alert."

The complaint, citing witnesses, alleges that Ferrante requested the purchase of cyanide. It was delivered one day later, on April 16.

Cyanide is a naturally occurring toxic substance that can be found in seeds of different plants. It is widely distributed throughout research laboratories as a chemical used in scientific experiments.

Cyanide interferes with the ability of the body to use oxygen to produce energy, which can lead to rapid death.

According to the complaint, text messages were found between the couple on April 17, the day Klein fell ill. The exchange included Ferrante suggesting creatine to Klein in hopes of stimulating egg production.

When paramedics arrived, they found the victim on the floor of the kitchen with a plastic bag containing creatine.

According to Karl Williams, chief medical examiner of Allegheny County, there is no connection with creatine and fertility. Creatine is a supplement that bodybuilders uses to increase body mass, Williams said.

Sole and legal custody of Ferrante's child has been placed with the maternal grandparents, according to a statement form the district attorney's office.